The mission-critical system which must not go down easily, such as a mission-critical system of a financial institution, for example, is generally configured as a cluster, that is to say, a redundant system. Such a redundant system is operated in such a way that an active-system apparatus and a standby-system apparatus mutually monitor each other, and the standby system is switched to serve as an active system in response to detection of an anomaly in the active system.
As a technique of monitoring and operating a redundant system described above, the following techniques have been proposed, for example. To be specific, in one example of the proposed techniques, a client terminal executes the steps of: accessing a dual network management system to obtain a monitoring program for monitoring a system switching; activating the obtained monitoring program; and causing the activated monitoring program to periodically access the dual network management system and to detect a switching of the network management system from a response from the network management system (see Patent Literature 1).